Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$56.61	4.729%	$59.2871	$59.29	$59.30	$59.30
Purchase #2	$240.77	12.793%	$271.5717	$271.57	$271.55	$271.60
Purchase #3	$249.86	8.413%	$270.8807	$270.88	$270.90	$270.90
Purchase #4	$53.39	9.175%	$58.2885	$58.29	$58.30	$58.30
Purchase #5	$107.47	7.151%	$115.1552	$115.16	$115.15	$115.20
Purchase #6	$85.92	13.210%	$97.27	$97.27	$97.25	$97.30
Purchase #7	$166.35	4.637%	$174.0636	$174.06	$174.05	$174.10
7 purchase totals =	$960.37		$1,046.5168	$1,046.52	$1,046.50	$1,046.70